SuperSpec

Friday, 26 May 2017

Lambda Sensor

On the cooling test run the Lambda sensor was a pain in the neck. Here is a picture of the
last 30 minutes of the trip.

The first part of the trip was fine as the ECU quickly decided the sensor
was useless so went into open loop (Status=zero) and as we all know
the car still goes perfectly in the 'limp home' mode. The problem
occurred when I stopped for petrol (18 mins on the graph). The ECU
re-started in closed loop and because the sensor was initially OK it
stayed in closed loop. The problem, as ever, was when the lambda
sensor started sulking the ECU continued to use the output and
stayed in closed loop. So for most of the journey back home she
was sluggish, popping and banging from the exhaust and well down on
power. Then there would be a sudden surge in power as the sensor
started working and she ran beautifully, only to revert to poor
running when the sensor failed again. Very frustrating and I am
seriously thinking of disconnecting the sensor until I get round to
replacing it.

This screen shot of the Short Term Fuel Trim shows the problem.Because the ECU is trying to use the 'duff' data from the sensor, it
totally wrecks the fuel/air ratio, causing all those symptoms (I
think it stops at -25% to avoid ruining the engine).
Still, enjoyed driving in a short sleeve shirt for the first time
this year, and
my new Power Steering system worked perfectly as well.